A. Field of the Invention
This invention relates generally to the field of computer-interactive methods for diagnosis, care and treatment planning, therapeutics and treatment monitoring in the medical arena, including orthodontics and in particular to a computerized and interactive method of facilitating placement and evaluation of orthodontic appliances for treatment of a patient. In the method, the patient's teeth are represented in a computer as three-dimensional virtual objects. The orthodontist may simulate various types of appliances, their placements and tooth movement, analyze the simulation results, and thereby explore possible treatment options that would produce the desired results.
B. Description of Related Art
In orthodontics, a patient suffering from a malocclusion is typically treated by bonding brackets to the surface of the patient's teeth and placing archwires in the slots of the brackets. The bracket-archwire interaction governs forces applied to the teeth and defines the direction of tooth movement. Therefore, the placement of brackets on the patient's teeth plays a crucial role in the outcome of the treatment. When the brackets are placed properly, and the archwire bent accordingly, the desired results from the treatment are achieved in the most efficient manner; otherwise, the treatment could last much longer.
Typically, orthodontists utilize their expertise to first determine a three-dimensional mental image of the patient's current physical orthodontic structure and a three-dimensional mental image of a desired physical orthodontic structure for the patient, which may be assisted through the use of x-rays and/or models. Based on these mental images, the orthodontist further relies on his or her expertise to place, for example, the brackets and/or the O-rings on the teeth. Unfortunately, in the oral environment, it is impossible, using human sight, to accurately develop a three-dimensional mental image of an orthodontic structure due to the limitations of human site and the physical structure of a human mouth. Further it is humanly impossible to determine an ideal bracket location to achieve the desired orthodontic structure based on mental images. It is also extremely difficult to manually place brackets in the estimated ideal location, to control bonding agent thickness, ligation forces, manufacturing tolerances, and biological changes.
Alternatively, orthodontists have the possibility of taking plaster models of the upper and lower jaws, cutting the model into single tooth models and sticking these tooth models into a wax bed, lining them up in the desired position, the so-called set-up. The next step is to bond a bracket at every tooth model. This would tell the orthodontist the geometry of the wire to run through the bracket slots to receive exactly this result. The next step involves the transfer of the bracket position to the original malocclusion model. Such physical modeling would provide only very limited treatment simulation capability, and could be time consuming and expensive.
Additionally, orthodontists may utilize commercially available bracket height-measuring gauges or a set of dividers, such as for example marketed by Ormco corporation, 1717 West Collins Avenue, Orange, Calif. 92867, USA, to guide them in determining and marking the bracket placement positions on teeth. Such gauges can be used in conjunction with a physical model of the patient's teeth as well as with the patient's real teeth. However, when the patient's teeth are crooked and hard to measure, e.g., with perverted axial inclination, usefulness of such gauges could be limited; and may not yield the desired accuracy in placing the brackets. Furthermore, such physical gauges are generally limited in capability in that they are intended for measurements solely from good cusp tips. Also consistency in measurements is critical, which may be difficult to achieve in manual measurements. The gauge positioning is likely to influence the measurement.
As described, the practice of orthodontic is very much an art, relying on the expert opinion and judgment of the orthodontist. In an effort to shift the practice of the orthodontic from an art to a science, many innovations have been developed. For example, U.S. Pat. No. 5,518,397 issued to Andreiko, et. al, provides a method of forming an orthodontic brace. Such a method includes obtaining a model of the teeth of a patient's mouth and a prescription of desired positioning of such teeth. The two-dimensional contour of the teeth of the patient's mouth is determined from the model. Calculations of the contour and the desired positioning of the patient's teeth are then made to determine the geometry (e.g., grooves or slots to be provided in the brackets) are created. Custom brackets including a special geometry have been created for receiving an arch wire to form an orthodontic brace system. Such geometry is intended to provide for the disposition of the arched wire on the bracket in a progressive curvature of a horizontal plane and a substantially linear configuration in a vertical plane. The geometry of the bracket is altered, (e.g., by cutting grooves into the bracket at individual positions and angles and with particular depth) and in accordance with such calculations of the geometry of the patient's teeth. In such a system, the brackets are customized to provide three-dimensional movement of the teeth once the wire, which has a two-dimensional shape, (i.e., linear shape in the vertical plane and curvature in the horizontal plane) is applied to the brackets.
To assist in the accurate placement of brackets on a tooth, a jig may be utilized. One such jig is disclosed in U.S. Pat. No. 5,368,478 issued to Andreiko, et. al which provides a method for forming jigs for custom placement of orthodontic appliances on teeth. In general, the '478 patent teaches that each jig is provided with a surface conforming to the contour of the tooth to which they are to be mounted. Another surface of the jig engages the bracket to hold it in the proper position and orientation for mounting to the tooth and spaced in relation to the contour surface to precisely locate the jig on the tooth. The jigs are particularly useful in positioning brackets of custom appliances desired to the individual anatomy of the patient and requiring custom positions of the brackets on the teeth. While the '478 patent discloses a method for forming a jig, such jig utilization still keeps the bracket as the focal point of the orthodontic treatment and provides no feedback mechanism regarding actual placement of the bracket. Further, the '478 patent does not allow for variables associated with tooth movement such as static, dynamic, or psychosocial mechanical and/or biological changes.
U.S. Pat. No. 5,431,562 to Andreiko et al. describes a computerized, appliance-driven approach to orthodontics. In this method, first certain shape information of teeth is acquired. A uniplanar target archform is calculated from the shape information. The shape of customized bracket slots, the bracket base, and the shape of an orthodontic archwire, are calculated in accordance with a mathematically-derived target archform. The goal of the Andreiko et al. method is to give more predictability, standardization, and certainty to orthodontics by replacing the human element in orthodontic appliance design with a deterministic, mathematical computation of a target archform and appliance design. Hence the '562 patent teaches away from an interactive, computer-based system in which the orthodontist remains fully involved in patient diagnosis, appliance design, and treatment planning and monitoring.
U.S. Pat. No. 5,879,158 to Doyle et al. describes an orthodontic bracketing system and method. To start with, from a negative impression of a patient's teeth, a positive hard duplicate pattern such as a stone model of the teeth is made. A digitized three dimensional coded image of the teeth is then generated by means of a coordinate measuring machine or by laser scanning. The central axis of each tooth is then displayed in an exploded image of the set of teeth and each tooth is moved in virtual space to a desired position and orientation using torque, tip and angulation values as well as in/out position information provided by the selected orthodontic bracket system. The optimum position of each tooth-mounted orthodontic appliance bracket and its attachment point to its associated tooth for moving the tooth to a desired orientation and position is then determined using the digitized coded images of each tooth including its central axis in its initial and final desired position and orientation. Using this bracket attachment information for each tooth, the shape and contour of a bracket attachment jig is determined for each tooth and this information in digital form is used to fabricate a plurality of such jigs under computer control such as by using a computer numeric control (CNC) milling machine for attaching an off-the-shelf, conventional orthodontic bracket to each tooth. Conventional archwires attached to the upper and lower optimally positioned brackets urge each tooth to its respective desired position and orientation with minimal subsequent manipulation and adjustment of the archwires by the orthodontist.
U.S. Pat. No. 6,334,772 to Taub et al. describes a method, system and device for positioning and fixing an orthodontic element on a surface of a tooth. The positioning of the element on a tooth is accomplished by: bringing the element into proximity of the tooth while continuously capturing an image of at least the tooth or of the element, and an image of both, once the tooth and the element are proximal to one another; transmitting the image or its representation to a display for displaying a real-life image of the captured image or representation together with indicators providing guidance information on intended position of the orthodontic element on the tooth's surface; positioning the element on a tooth's surface according to the indicators such that the element's position coincides with the intended position; and fixing the element onto the tooth.
U.S. Patent Application Publication No. 2003/0143509 A1 to Kopelman et al. describes a method and system for providing information for correct placement of one or more brackets on one or more corresponding teeth according to a predetermined treatment scheme. A virtual representation of a three-dimensional teeth arrangement of one or both jaws of the individual with brackets placed on said teeth is obtained, wherein the position and orientation of the brackets on said teeth being designed so as to achieve a desired treatment outcome. The virtual representation is processed to generate an output data, the output data driving a display, such as a computer monitor or a printed “hard-copy”, to display an image of at least one tooth with a bracket thereon, the displayed image having three-dimensional qualities indicative of said at least one tooth as viewed from a defined viewpoint. The invention can be applied to the placement of brackets onto the buccal side of the teeth as well as onto the lingual side of the teeth.
Unfortunately, the current innovations to change the practice of orthodontic from an art to a science have only made limited progress. Placement of each bracket on a corresponding tooth is critical. A misplacement of a bracket by a small amount (e.g., an error vector having a magnitude of a millimeter or less and an angle of a few degrees or less) can cause a different force system (i.e., magnitude of movement and direction of movement) than the desired force system to be applied to the teeth. As such, the tooth will not be repositioned to the desired location.
Therefore, to further enhance the accuracy of orthodontic treatment a need exists for enabling the practitioners by facilitating modeling of accurate placement of orthodontic appliances and simulating their impact on teeth movement in conjunction with matching archwire configurations.